This invention relates to a measuring device, and more particularly to an electrical measuring device.
Still more particularly, the invention relates to a digital electrical measuring device. Specifically, the invention relates to a digital electrical length or angle measuring device, particularly an absolute coded length or angle measuring device.
Precision measuring devices are known for measuring geometric values, for example lengths or angles, or values which are derived therefrom such as speed, acceleration, or the like. Such precision measuring devices are used, inter alia, in machine tools, in controls, in testing and measuring apparatuses, in automated manufacturing facilities and in industrial robots.
Length measuring devices are known in various types of constructions and functions. German Published Application No. 2,744,699 contains a review of the various position measuring devices which are known in the art. This published applicatin also discloses a dual scanning method which serves for establishing an absolute connection between two measuring systems of differential resolution, such as a fine measuring system and a coarse measuring system.
Another dual scanning method for coupling two position measuring systems is discussed in an article by H. Walcher in "Archiv fuer technisches Messen und industrieller Messtechnik, ATM", August, 1971, pages R89-R104, revision 427.
In the case of measuring systems of higher resolution and in the case of the coupling of two measuring systems of different resolution the space requirements and the technical requirements increase strongly due to the dual scanning method, since the electronic circuitry for handling the measured results also increases substantially. The requirements for tracers, scanners and electronic circuitry is further increased when it is additionally necessary to provide test bits. Such testing circuits are known from German Allowed Application No. 2,748,320 and from German Published Application No. 2,825,038.